The present invention relates to a housing for a fluid dynamic bearing device. The fluid dynamic bearing device having this housing is suitable for use in a spindle motor of an information apparatus, for example, a magnetic disk apparatus, such as an HDD or an FDD, an optical disk apparatus, such as a CD-ROM, a CD-R/RW, or a DVD-ROWM, or a magneto-optical disk apparatus, such as an MD or an MO, a polygon scanner motor of a laser beam printer (LBP), a color wheel of a projector, or a small motor of an electric apparatus, such as an axial flow fan.
Apart from high rotational accuracy, an improvement in speed, a reduction in cost, a reduction in noise, etc. are required of the motors described above. One of factors determining such requisite performances is a bearing supporting a spindle of the motor. In recent years, as such the bearing, use of a fluid dynamic bearing superior in the above requite performances is being considered, or such the fluid dynamic bearing has been actually put into practical use.
The fluid dynamic bearings of this type can be roughly classified into dynamic pressure bearings equipped with a dynamic pressure generating portion for generating a dynamic pressure in a lubricating fluid in a bearing gap, and so-called cylindrical bearings equipped with no dynamic pressure generating portion (bearings whose sectional configuration is circular).
The above-mentioned fluid dynamic bearing device is composed of components, such as a housing, a bearing sleeve, and a shaft member. As information apparatuses are improved in terms of performance, efforts are being made to enhance dimensional precision and assembly precision of their components in order to secure a high rotational performance as required. On the other hand, due to tendency of information apparatuses to be reduced in price, there is an increasingly strict demand for a reduction in the cost of fluid dynamic bearing devices of this type. Nowadays, to meet this demand, as disclosed in JP 2003-314534 A, some fluid dynamic bearing devices have housings, which are constituent components thereof, formed of resin materials.
For the method of fixing another member such as a bearing sleeve or a seal member, to an inner periphery of such the resin housing, it is desirable to be the method involving a press-fitting force, such as press-fitting or press-fitting/adhesion (press-fitting through the intermediation of an adhesive), taking into account the fixing force and temporary positioning. However, as compared with a metal housing, the resin housing is inferior in creep resistance, so the press-fitting force, that is, the fixing force for the another member, undergoes a considerable deterioration with time. Thus, when an excessive load, such as drop impact, is applied to the bearing device, there is a fear of problems, such as deviation of fixing positions of the another member with respect to the housing and a deterioration in bearing performance